Various devices are currently known to increase the aerodynamic efficiency of a truck, semi trailer, or other large moving object. It has long been recognized that the rectangular high profile shape of these vehicles and the speeds necessary for travel increase aerodynamic drag. Reducing aerodynamic drag will significantly reduce overall fuel consumption and harmful air emissions. The present disclosure relates to add-on inflatable air deflectors for the rear surface or aft face of a transport trailer, for example, air deflector boattails that can be mounted to trailers that use swing or roll-up doors on a box van or other trailers which typically operate at speeds routinely in excess of 35 mph.
Inflatable drag reducers have been described (e.g. McDonald (1977) U.S. Pat. No. 4,006,932, Ryan (1998) U.S. Pat. No. 5,823,610, Andrus (2002) U.S. Pat. No. 6,409,252), and are more practical than rigid versions (e.g. Lechner (1994) U.S. Pat. No. 5,375,903, Switlik (1996) U.S. Pat. No. 5,498,059, Boivin (2001) U.S. Pat. No. 6,257,654 B1), because inflatables are light-weight and can be collapsible to a very thin state so as not to interfere with complete trailer door opening which is important because of the limited room to maneuver at most loading docks. However, given that the majority of standard long-haul box van transport trailers are typically a double door (i.e. swing door) configuration, it is beneficial to have a drag reducer with two separate portions (i.e. a separate portion associated with each door). Additionally, the two separate portions should, as a coordinated unit, provide beneficial drag reduction. Alternatively, drag reducers should also accommodate single doors, i.e. rollup doors, having a single continuous opening spanning the rear of the trailer.
It is of course well known that the box shape of trailers of tractor-trailer vehicle combinations, and other truck-trailer combinations, is the result of a need to optimize cargo space therewithin, and it is likewise well known that the boxlike configuration is not aerodynamically efficient. The aerodynamic drag resulting from the box shape accounts for a considerable percentage of the fuel consumption of large trucks and tractor-trailer vehicle combinations during highway operation thereof. In an effort to improve the operating efficiency of such vehicles, the tops of the cabs of trucks and tractors and the upper forward edges of both the tractor and trailer have been streamlined by using a wide variety of body contours and wind or air foil devices. Air foils mounted on the cabs of trucks and trailers can be rigid and permanent in character in that the areas on which the air foils are mounted typically do not need to be accessed in connection with use or operation of the vehicle. On the other hand, the rear ends of trailers do have to be accessible in that they are closed by doors providing access to the interior thereof for loading and unloading purposes. Accordingly, aerodynamic drag reducing devices designed for use on the rear end of trailers (i.e. boattails) can be hinged panels with guiding tracks and/or pulleys to allow folding during door opening, detachable, and/or provided individually on the doors of the trailer. For some applications, if the device is not going to be used it would have to be stored somewhere in the vehicle or, merely deflated and allowed to remain on the door. Hinged panels require manual intervention and may be subject to mechanical maintenance and other servicing due to snow and ice buildup preventing the operation of the hinged panels. Removal and storage is a labor intensive and time-consuming operation in addition to requiring storage space.
For these reasons inflatable drag reduction boattails have become exemplary because they are light, inexpensive, and may be collapsed without the use of an excessive number of moving parts. However, despite the advantages of inflatable boattails the prior art designs failed to solve the problems associated with loading and unloading the tractor-trailer because the devices are attached as one unit to the back, they are cumbersome to use, or they are excessively large resulting in excess material/weight, higher cost, require driver/operator interaction, and/or produced inferior aerodynamic performance.
The devices currently known to increase aerodynamic efficiency, while somewhat effective, suffer from a number of other drawbacks. The previous devices, heretofore known, that have been attached to the back of trailers often include mechanical fold out panels, inflatables with ram air assist orifices, and very large air volume inflatable devices. The results respectively require: manual operation of the panels that are also subject to snow and icing operational problems; ram air inlet orifices that can clog with debris, snow or ice and with un-regulated internal pressure; and inflatables with huge air volume and footprints that covered the majority of the rear trailer surface but not aerodynamically profiling the full trailer side and also requiring large air blower systems. Similarly, other devices do not allow for the convenient loading and unloading of the trailer's cargo because they consist of a single attached unit that must be removed, or manually activated to fold, including complex mechanical systems that require maintenance. Furthermore, often the prior art devices are ineffective in that they provide little drag reduction when in use, are costly to produce or install, and/or encounter door opening limitations due to their large size.
Accordingly a need exists for an improved aerodynamic drag reduction device for tractor-trailers, trailers, box trucks, etc.